Transcription factor Mbp1 controls β-glucan synthesis in basidiomycete Pleurotus ostreatus
Hayase Kojima1, Yuitsu Otsuka1, Kim Schiphof1, Moriyuki Kawauchi1*, Kenya Tsuji1, Akira Yoshimi1, Chihiro Tanaka1, Shigekazu Yano2, Takehito Nakazawa1, and Yoichi Honda1
1Graduate School of Agriculture, Kyoto University, Kitashirakawa-oiwakecho, Sakyo-ku, Kyoto 606-8502, Japan
2Graduate School of Sciences and Engineering, Yamagata University, Jonan, Yonezawa, Yamagata 992-8510, Japan
The mycelia of white-rot basidiomycete mushrooms are gaining more attention as a sustainable resource because they can grow on wood and agricultural wastes, and are being used as an alternative resource for meat, leather, and other materials. To improve the quality and expand the applications of mushroom-derived materials, it is necessary to modify mycelial properties such as texture and strength. Cell walls are thought to be important in regulating these properties, however, cell walls of basidiomycetes are shown to be quite different from those of ascomycetes in their composition and structure, and are currently poorly understood. To modify mushroom cell walls, understanding the transcriptional regulation of cell wall synthesis in basidiomycetes is indispensable. In this study, we analyzed the function of a transcription factor Mbp1 that may be involved in the cell wall integrity pathway in Pleurotus ostreatus. Comparison between a mbp1 disruption strain (Δmbp1) and wild type (WT) highlighted significantly thinner cell walls in Δmbp1. A cell wall component analysis demonstrated the amount of β-glucan decreased while the relative percentage of chitin was unchanged in Δmbp1. Moreover, a qRT-PCR analysis showed the relative expression levels of all β-glucan synthases decreased significantly.Finally, when cultivated on a static liquid medium, the Δmbp1 mycelium mat was inflexible and easily cracked compared to that of WT. In conclusion, Mbp1 has an essential role in regulation of β-glucan synthesis in this fungus, and genetic manipulation of mbp1 can be used to modify the properties of cell walls and eventually materials from mycelia.